1. Field of the Invention
The present invention relates generally to a self-contained portable air movement and purification system, and more particularly, to such a system which is capable of removing particulate and bacterial contaminants and generally purifying the air of a contained environment.
2. Description of the Prior Art
A wide variety of air filter systems are presently available for use. These systems typically include a fan arrangement for circulating air, and a filter stage or perhaps multiple filter stages disposed in the air path so as to filter or otherwise purify air flowing therethrough. The air filters differ widely in their volume capacity, their efficiency of filtration, airflow directions, and their ease of portability.
Several different types of filtering stages are available for use in present day air filter systems. The air filter stage may have, for example, an electrostatic precipitator type of element which charges dust or other airborne contaminants and attracts the airborne contaminants to an electrically charged grid. In general, electrostatic air filter stages are expensive to fabricate and install, and they often require relatively costly maintenance. In addition, there is a substantial electrical power requirement over and above that needed for maintaining an air flow through the filter stage.
As another general type of air filtering, one or more layers of porous media alone are disposed in an air flow path for "mechanically" filtering or trapping airborne particles contained in the air flow. In general if a greater efficiency of filtering or germ or odor removal is desired, additional stages or filtering layers are added. This, however, multiplies the cost of the initial filtering stage and frequently results in a significant pressure drop across the filter, thus requiring a higher fan capacity with greater electrical consumption for maintaining a desired air flow.
Users of air filter systems are frequently concerned about the amount of air treated by a filter stage in a given time period, for example, requiring several changes of air volume in a room, for each hour of operation of the air filter system. This concept of room air filtering is frequently expressed as a number of "room air changes" per hour. For purposes of comparison, building codes frequently require that public restaurants and similar public buildings have at least one or two air changes per hour, meaning that a volume of air equal to that required to fill a room is completely removed and replaced by fresh air at least once or twice each hour that the room is open to the public. The present invention is particularly concerned with providing an air filter system capable of filtering the air in an entire room on the order of several times per hour.
In a practical air filter system, much more is needed than simply providing sufficient fan capacity to "turn over" the air filling a room at the desired rate. For example, the efficiency of the filter media, over its life span must be considered. As air is caused to flow through a porous filter media, airborne particles and the like are trapped in the filter media, thus reducing its porosity and increasing the resistance of the air flow through the filter stage.
Other types of air filtering media may be provided which react with dissolved chemicals suspended in the air. Such filters frequently operate by adsorbing the chemical contaminants by collecting those contaminants in condensed form on the media surface. The adsorbed contaminants have the potential for changing the surface properties of the air filter media and in particular, have the potential of changing the resistance to air flow through the media. While an air filter stage could be "oversized" so as to provide a minimal acceptable air conductance at the end of its useful life, the cost of the air filter media in the stage rises significantly as does the size of that filter stage.
In addition, special considerations must be given to particular types of air filter media. For example, activated charcoal is a popular type of air filter media in use today and is frequently utilized as a bed of charcoal particles through which an air flow is conducted.
Presently, there exists a need for a high volume portable room air filter unit having at least a minimum filtering efficiency for types of contaminants frequently encountered in everyday situations. Of particular interest is the availability of an effective portable air filter system for use in rooms frequented by the public, in smoke-filled offices, and especially in residences of people suffering from asthma or allergies. However, in order to be practical in use, the air filter system should be sufficiently small in size and readily portable so that it can be moved from room to room and so that it can also be easily moved within a room without significantly altering its operation or adversely affecting the comfort of occupants of the room. Several arrangements of portable room air filters have been proposed, yet the need for further improvements still exists.
Pollens, lung damaging dust, smoke, bacteria, viruses and any one of a number of other irritants and micro-organisms are quite likely in the air that everyone breathes. These irritants are carried by the wind, on people's clothing, on the hair or feathers of a pet, or sprayed about by a sneeze or a cough. Contact with these irritants is almost inevitable. Also, for persons plagued by the miseries of emphysema, asthma, hay fever or other allergies, contact with irritants and micro-organisms means unpleasant discomfort and usually sleepless nights. Although different types of air purifiers presently exist, they are not completely effective in removing these irritants and micro-organisms from the air. Further, existing air purifiers do not provide the combination of effective removal of these contaminants along with the provision of a germicidal chamber for killing bacteria and virus. Specific examples of the prior art relating to air movement and purification systems will now be considered.
U.S. Pat. No. 5,069,691 to Travis et al. discloses a portable vacuum and air filtration unit for cleaning heating, ventilation, and air conditioning ductwork in residential and commercial buildings. Filtered air is exhausted into the room in which the unit is located.
U.S. Pat. No. 4,900,344 to Lansing, U.S. Pat. No. 4,787,922 to Kulitz, U.S. Pat. No. 4,737,173 to Kudirka et al. and U.S. Pat. No. 4,531,956 to Howorth all disclose portable filtration devices for workplaces and the like. Howorth is of particular interest in providing a sterile air zone for surgery and surgical instruments. However, in each instance the devices are relatively short of stature and do not adequately provide separation of the clean exhaust air from the soiled intake air.
U.S. Pat. No. 4,749,385 to Brunner et al. discloses apparatus for providing clean and heated air simultaneously to a workplace such as on a production line for the manufacture of cathode ray tubes. Airflow is directed through a HEPA filter and an infrared heater and onto a panel assembly for the cathode ray tube. Ambient air is drawn into the apparatus through an annular intake surrounding a circular exhaust.
U.S. Pat. No. 4,909,815 to Meyer discloses mobile air cleaning apparatus especially suited for use in an automotive vehicle repair and/or assembly plant. Filtered air is directed downwardly over the surface of the vehicle, then captured at a location beneath the vehicle for return and additional filtration.
U.S. Pat. No. 3,299,620 to Hollingworth discloses apparatus for the treatment and purification of air which utilizes a liquid spray for cleansing the air of particulate matter.
U.S. Pat. No. 4,210,429 to Golstein et al. discloses an air purifier which incorporates a number of features improved over the earlier mentioned references including its relative height and the use of germicidal lamps. Nonetheless, the present invention is deemed to incorporate significant, patentable improvements thereon which will be related below.
A more recent development is disclosed in commonly assigned U.S. Pat. No. 5,616,172 to Tuckerman et al. which discloses a self contained air movement and purification system focused on infection control. The system of that invention comprises an elongated upright enclosed housing including a base module, side walks, and an upper module. A fan intermediate the base module and the upper module draws unclean air from a room containing the system through the base module, then discharges a purified air stream from the upper module. The base module includes a downward facing air intake opening spaced from the floor. A pair of pre-filters are disposed on the base module in stacked relationship for trapping relatively large particulate matter from the entering air stream. The upper module includes a discharge grille opening to the environment with angled louvers for guiding and re-directing the purified air stream from a HEPA-type filter into an inclined stream, flowing proximate to and along the ceiling of the room in which the system is located. A germicidal chamber intermediate the pre-filters and the fan contains a plurality of elongated and longitudinally extending ultraviolet germicidal irradiation lamps. Because of the remoteness of the upper module from the base module, undesirable mixing of unclean and purified air is minimized. In another embodiment, the discharge grille has a first opening with angled louvers as in the first embodiment and a second opening to which an attached conduit leads to an exterior region outside of the room to thereby create a negative pressure in the room in relation to the exterior region.
It was with knowledge of the foregoing state of the technology that the present invention has been conceived and is now reduced to practice. The actuation and deployment concept embodied by this invention is different from all of the devices reviewed above.